The invention relates to electrical circuit devices, and particularly to a method for anchoring and connecting lead wires to such devices.
In recent years there has been an increase in the usage of circuit devices comprising substrates of ceramic material such as alumina, steatite or other materials, wherein at least one surface of the substrate includes a deposited thick or thin film electrical circuit. The devices are generally modular and may include, in addition to resistive and capacitive elements, the addition of discrete components to provide hybrid circuits. It will be obvious that means for terminating the electrical circuitry is of equal importance to the circuitry itself in order to provide an acceptable unit. Circuits fundamentally depend upon the integrity of electrical continuity through the termination and lead wires required for connection to printed circuit boards or other circuit components. Various developments have brought forth techniques for terminating, each of which has been designed to provide the necessary electrical continuity with the circuit and strength to achieve proper pull force at the connection between the lead wire and the termination of the circuitry. In addition, the connection must be solid and stable so as to minimize electrical "noise" problems.
Terminating techniques and provisions of terminal leads have been illustrated in various patents, most of which have been reviewed in U.S. Pat. No. 3,873,890 issued to Beckman et al and assigned to the same assignee as the present invention.
The device and method disclosed herein, although having application elsewhere, are principally related to so-called SIP (single in-line packaging) devices which are generally arranged to be supported in a position substantially normal to the plane of a printed circuit board or other mounting surface. Such devices may contain as many as seven or eight spaced apart lead wires closely positioned relative to one another.
The above-mentioned U.S. Pat. No. 3,873,890 teaches the insertion and retention of lead wires into a side of a ceramic substrate having an elongated groove divided into juxtaposed alternately distended and constricted portions, the constricted portions being adapted to receive the end portion of relatively flat lead wires. The constricted portion is metallized prior to receiving the lead wires and the lead wires are then inserted and soldered in place. The construction taught by Brady in his U.S. Pat. No. 3,346,774 disclosed a device which utilizes a substrate having lead wires anchored in cavities are of a size insufficient to freely receive the lead wires. The lead wires of Brady are forced into the cavity of the substrate to fixedly secure the lead wire directly to the substrate. The lead wire is further soldered in place to previously deposited metallized areas which areas include the entrance to the said cavities.
The Ragan U.S. Pat. No. 3,277,232 teaches a means of terminating an electrical circuit device with openings formed to traverse a substrate from end to end, and which substrate is arranged to receive oppositely disposed lead wires. Each lead wire has an end upset or bent to provide an obstruction externally of the substrate, which bent or upset headed portion is secured to the substrate by means of solder adhering to a metallized area, which is also connected to an electrical circuit disposed on the substrate.
Except for the Beckman et al patent, most previously developed devices were designed to receive individual leads, whereas Beckman et al and the device of the present invention are arranged to take advantage of "lead frame" construction, wherein a plurality of integrally formed leads project laterally from a common carrier portion of the frame. This type of construction lends itself to use in automated assembly, insertion, soldering and trimming apparatus. Previous devices suggest individual lead insertion techniques. Further consideration of the present disclosure, however, will reveal that although the best mode is considered to be in the form of so-called lead frame assembly, the invention may also utilize techniques of individual insertion of lead wires.